Metallic powder composition



ited States Patent 3,102,024 METALLIC POWDER COMPGSITEGN Alfred P.Knapp, Jackson Heights, N.Y., assrgnor to Knapp Mills Incorporated, LongIsland City, N.Y., a corporation of New York No Drawing. Filed Apr. 30,1958, Ser. No. 731,896

3 Claims. (Cl.75.5)

This invention relates to putty-like material and particularly to ametallic structure of powder particlescombined in plastic form to bemolded into various shapes and act as a seal, intercepting and blockingoff injurious radiation.

'This isa continuationimpart application based upon original applicationSerial No. 349,565, filed April 17,

-1953, now Patent 2,833,664, issued May 6, 1958, for

Metallic Powder Composition.

The object of the invention is to provide a metalcarrying puttyconcentrating the metallic content to high density to serve as anefifective barrier and seal against injurious radiations.

In the manufacture of equipment and buildings for atomic energy work,forinstance, it is vitally important to avoid leakage of theresultantradiation. In spite of the care exercised andthe expense involved,cracks and crevices are unavoidable and sometimes develop in use.

The metallic putty of my invention supplies an inexpensive, convenientand reliable seal for these openings,

simplifying the original structure and avoiding the necessityfof costlytime-consuming repairs where leaks develop in use.

In the formation of the putty a metallic powder of protectiveray-absorbing metal, such as lead, is mixed with a relatively slightamount of an oil or grease, acting For example, of

for a given thickness of the putty barrier. This increase is oftencritical rendering the material usable in situations where it wouldotherwise fail. The increase may be from lower density ranges to thecompacting for any density desired in the final product.

The relatively greater increase in absorption over the mere gain intotal quantity of interposed metal may be due to the greatereffectiveness of the coalesced particles in blocking the paths of therays. Whatever the explanation may be, there is an unexpectedimprovement in the concentrated structure rendering it far moreeflicient in absorption of the injurious rays.

For example, a normal lead putty mixture of the above ingredients havinga density in the range of 2 to 6.5 (grams per cubic centimeter), afterrunning through an extrusion under high pressure of five hundred poundsper square inch, has its density increased to over 9 and the resultingputty on microscopic examination shows its lead ing envelope.

or the like.

ice

Other agglomerating procedures such as beating, grinding, hammering andthe like may be employed depending on the materials and quantitiesinvolved. The important object is to bring the density of the putty ashigh as possible while still maintaining its pliancy so that it may bepressure-shaped into the cracks and crevices to be filled. The number ofparticles involved in the agglomerates will vary widely and theindividual agglomerates themselves are intermediately malleable in that,while firmer than the particle-vehicle mixture, they are more plasticthan the solid lead.

Other examples of typical mixtures operating in the same way when mixedand coalesced are 15% Quaker State Viscous-Lube, a pressure gun grease,with lead powder and 10% Dow Corning Fluid XF-ZOO, a silicone lubricant,with lead powder, both by Weight.- Any grease or oil acting to film themetal particles or agglomerates may be employed and the choice of thevehicle will depend on the locality and conditions of use, the crevicesto be filled, the temperatures involved, etc.

Instead of lead the powders of other metals such as tungsten may beused, ormixtures thereof may be resorted to where, for instance, thesofter acts as a bonding between the others. I

in the formation of the putty composition the precise proportionsbetween the metal powder and the binder material are not critical, theobjective being to employ as much powder as is practical. The oil orgrease used should be only suflicient to give a putty-like mass ofproper plasticity and a structure which will hold together and can beapplied as putty is used to fill cracks, crevices, seams, etc.

The high density is the important criterion, reflecting as it does thenecessary agglomeration of the great mass of the metal particles intoaggregates in which the particles are closely bound together. Thebinding forces between the particle surfaces will be thin molecularlayers of the oil or grease materialand also, preferably in larger part,the cohesion of the metal to metal contact of the metal surfaces as theyare forced together by the compressing action of the extrusion, beating,hammering The resultingstructure presents a cooperative barrier actionbetween the thus aggregated metal particles, greatly augmenting theefficiency of the absorption and simplifying the application of theputty and reducing the expense involved.

The extruded formations may dispense with the binder and the degree ofcompression will be controlled by the temperature and theintensity ofthe pressures applied, the metallic surface skin being developed as acontain- Particularly with powders of zinc, lead, tin and cadmium suchextrusion may be carried on at room temperatures. With other less softmetals it is desirable to raise the temperature, for instance, to aboutthe recrystallization level such'as 150 C. for aluminum and magnesium or200 C. for copper, silver and gold. In general the extrusion of anymetal at about its recrystallization temperature will give the interiorcompacting of the powder particles to about 70% to of the density of themetal of the powder, and simultaneously the extrusion will develop thesubstantially continuous particles in agglomerates of various groupingsin which the adjacent particles or establishing a bond of metal tometal.

metallic surface layer. The result is a bendable rod of suflicientplasticity to be readily pressed and molded into desired shape.

The powders may be a mixture of difierent metals.

In the extruded formation of the powdery material the metal particlestend to accumulate and concentrate at the surface of the rod-likeextruding mass developing a metallic surface skin by the weldingtogether of the particles under the pressures applied and the resultingattrition between the material andthe containing walls of the casing. Ametal tube formation is thus generated holding the. compacted materialwithin it and rendering the putty convenient and easy to handle andapply as plastic strips readily bent and compressed into tight andclosely fitting engagement with the crevices andv openings to be sealed.

Thecross sectional shape of the extruded stripsmay be of any desiredconfiguration, circular, triangular, recvantageous positioning andinterfitting with the surfaces of the parts of the apparatus to whichthey are applied,

'or of metal alloys. A soft metal powder such aslead may be mixed. withparticles of a harder metal, for

instance tungsten, toserve asa binder for the latter to correspondinglyreducetthe temperature tand pressurerret.

quired for the compacting procedures, and the invention in itsdevelopment of the ray absorption and plasticity attains substantially.the full protection of the solid metal but-in desiredshape. and plasticform. I

It involves a combination of critical features contributing to the finalray absorbent strip or putty formation.

The particle surfacing time cycle may consist of continuous orintermittent processing and aging to achieve the final stabilityrequired, depending upon the density of the ingredients and othercriteria as follows:

(l) Fineness.--The.metal (lead) should be in fine powder form' tostartwith. The finer the powder, the

greater the surface area involved per pound, and the I uthinner will bethe finally formed powder flakes in the 'ultimate product. 1

' tangular or more intricate designs adapted for most ad- I,

the resultant thinning of e film willten to spread it and make it easilydisrupted at the tiny area of contact and concentrated pressure withresultant cold weld which cannot be made in any other way.

"(5) Pressure.The pressure must b uffi i have the spreading flat ningeifect on the particles Suppl the energy. for the microscopic coldwelds.

I claim: I

l; A putty-like structured'metallic sealing material a having a handpressure responsive pliancy adapting'it to Y be handpres'sure-shapedinto'place to'intercept injurious radiation and consisting only of fine,protective ray- .absorbing metal powder particles worked and reshapedand-reformed together under pressure, said particles being largelycompacted and agglomerated together and joined v W atmetal-to-metalcontact areas into aiplastic" entirely metallic structure of aggregatesof various groupings of particles of shapes determined by .sai(l;wo'rking with a spreading and flattening of individual'metal-to-nietal' contacts between portions of the surfacesiof the saidparticles I developing metal-to-metal adherence at said contacts and acorresponding pliancy andauniform composition with an overall density ofthe plastic metal structure of 70% to 95% of the density of 'the metalof the particles'and forming a continuous barrier seal against radiationblocked by the metal of said particles.

2. A putty-like sealing material'as set forth in claim 1 in whichthereare soft inetal'powder particles which are of lead and the density ofthe plastic metal structure isat least 9.5.

3. A putty-like sealing material as set forth in claim 1 in which thereare metal particles of different metals that the localized energy .at'the minute areas of contact will form tinycold'weld's} I (4)Particlesurfacing Before the pressing operation the surfaces of themetal particles shouldbe conditioned to provide for metal-to :metalcontact. It is important that any surface oxide orother filming be verythin indeed so that as the particle is multilated' and hasits surfacearea correspondingly increased under the pressure,

forming a composition including particles ofa metal relatively soft incomparison with the metalfor metals. of theremaining particles.

References Cited the'fileof this patent UNITED STATES PATENTS h Thurston..'Mar. l, 1932 2,028,240 Palmer "Jan.21-, 1936 2,386,604 Goetzel i Oct.9, 1945 2,689,398 Gaut et al. 'Sept. 21, 1954 2,833,664 1958 Knapp -aMay 6,

1. A PUTTY-LIKE STRUCTURED METALLIC SEALING MATERIAL HAVING A HANDPRESSURE RESPONSIVE PLIANCY ADAPTING IT TO BE HAND PRESSURE-SHAPED INTOPLACE TO INTERCEPT INJURIOUS RADIATION AND CONSISTING ONLY OF FINE;PROTECTIVE RAYABSORBING METAL POWDER PARTICLES WORKED AND RESHAPED ANDREFORMED TOGETHER UNDER PRESSURE, SAID PRATICLES BEING LARGELY COMPACTEDAND AGGLOMERATED TOGETHER AND JOINED AT METAL-TO-METAL CONTACT AREAS TOPLASTIC ENTIRELY METALLIC STRUCTURE OF AGGREGATES OF VARIOUS GROUPINGSOF PARTICLES OF SHAPES DETERMINED BY SAID WORKING WITH A SPREADING ANDFLATTENING OF INDIVIDUAL METAL-TO-METAL CONTACTS BETWEEN PORTIONS OF THESURFACES OF THE SAID PARTICLES DEVELOPING METAL-TO-METAL ADHERENCE ATSAID CONTACTS AND A CORRESPONDING PLINACY AND A UNIFORM COMPOSITION WITHAN OVERALL DENSITY OF THE PLASTIC METAL STRUCTURE OF 70% TO 95% OF THESENSITY OF THE METAL OF THE PARTICLES AND FORMING A CONTINUOUS BARRIERSEAL AGAINST RADIATION BLOCKED BY THE METAL OF SAID PARTICLES.